1) 975=3*5*5*13;
1980=2*2*3*3*5*11;
НОД(975;1980)=3*5=15;
НОК(975;1980)=1980*5*13=128700;
2) 840=2*2*2*3*5*7;
2700=2*2*3*3*3*5*5;
НОД(840;2700)=2*2*3*5=60;
НОК(840;2700)=2700*2*7=37800;
3) 162=2*3*3*3*3;
432=2*2*2*2*3*3*3;
1440= 2*2*2*2*2*3*3*5;
НОД(162;432;1440)=2*3*3=18;
НОК(162;432;1440)=1440*3*3=12960;